Preparation of aromatic nitriles



Patented June 11, 194i:

UNITED srrcs ears.

- .2,20s,se1 PREPARATION or AROMATIU murmurs Arden Garrell Deem, Champaign, 111., and Wilbur Arthur Lazier, Wilmington, Del., assignors to E. I. du Pont de Nemours 85 Company, Willmington, DeL, a: corporation of Delaware No Drawing. Application December 6, 1938, Se-

rial .No. 244,232; In Great Britain May 27,

7 Claims.

issuedMarch .7, 1939, ofwhich this is a continuation-in-part, we havedisclosed a catalytic proc- M ass for the manufacture of aryl dinitriles, such as o-phthalonitrile, that comprises passing a gaseous mixture of ammonia and an aromatic orthodicarboxylic acid, anhydride, amide, or imide over a suitable dehydrating catalyst at elevated 2n temperatures. ,In this application we have pointed out that among the wide variety of contact materials that can be employed, those that are merely operable, in the sense that they produce phthalonitrilefrom phthalimide, and the like, in 25 mediocre yields, are to be distinguished from those, that fulfill requirements for economical .operation' on a large commercial scale. For ex ample, basic aluminum phosphate and basic aluminum sulfate are outstanding catalysts for this no process not only because they give o-phthalo nitrile inhigh yields, but because they are further characterized by aremarkable sturdiness, inertness toward the components of the gaseous reaction mixture, and by their sustained high cata- 35 lytic activity over long periods of, continuous operation.

. It is the object of this invention to provide an additional group of catalysts which may be em ployed successfully for the above purpose.

in We have found that the oxides of zirconium,

knowledge and belief was unknown prior to our discovery thereof. 55 Broadly speaking, our invention comprises producing aromatic dinitriles by bringing a gaseous mixture of ammonia and an aromatic dicarboxylic acid, anhydride, amide orimide into contact continuously. with a dehydrating catalyst selected from the group consisting of zirconium oxide, beryllium oxide, tungsten oxide, and vanadium oxide at elevated temperatures and essentially atmospheric pressure. A more ,full and complete description of our process is given in the following examples, which illustrate but do not otherwise limit the invention.

Example 1.-A stream of ammonia is passed at l the rate of 272 liters per hour througha tube containing 500 cc. of tungsten oxide catalyst main:

tained ata temperature of 400 C. Phthalic ari hydride is vaporized and passed with theammonia at the rate of 118.8 gm. per, hour. .Under these conditions the molecular ratio of ammonia to phthalic anhydride is 15:1,the spacevelocity is 580 volumes of gas per unit volume of'catalyst per hour, andthe contact time is 2.5,sec0nds.

The products issuing from the tube, are con densed in a suitable receiver, and consist of a slightly greenish solid mass having a pronounced odor of benzonitrile. The product obtained by processing 368.5 gm. of phthalic anhydride during a period of 3.1 hours is extracted with warm benzene until all soluble material is removed. The benzene insolubleresidue consists of 69.5 gm. of phthalimide, melting point 222 C., which is suitable for recycling in the process. is evaporated from the benzene solution and the residue subjected to vacuum fractional distillation. There is obtained 13.1 mm. of pure benzonitrile, boiling point 88 (1/26 mm. and 222 gm. of ertho-phthalonitrile, boiling point 150 to 152 C./l.0 mm., melting point 140 to 141 C. The molecular conversions to phthalimide, phthalonitrile and benzonitrile are 18.9%, 69.7%, and 5.1%, respectively.

Example 2.-Five hundred cc. of vanadium oxide-on-alundum catalystv inthe form of small lumps is charged into a vertically mounted catalyst tube and heated tofia temperature of 400 C. Ammonia is passed through the catalyst bed at the rate of 272 liters per hour. Phthalic anhydride is vaporized and passed in with the ammonia at the rate of 106.8 gm. per hour during a period of twelve hours. Under these conditions the ammonia phthalic anhydride ratio is 16.911, and the contact time is 2.5 seconds. The gaseous products issuing from the reactor tube are condensed to form a faintly yellow powder, which is treated according to the procedure of Example I to recover ortho-phthalonitrile, phthalimide, and

The solvent;

] hours.

' beryllium benzonitrile. From 1281.6 gm. of phthalic anhydride processed, there is obtained 686 gm. of

*phthalonitrile, 435 gm. of phthalimide, and 32 gm. of benzonitrile. These amounts correspond respectively to molecular yields of 61.9%, 34.2%, and 3.6% of theory. The recovered phthalimide is of excellent quality and after grinding is suitable for mixing with a fresh charge of phthalic anhydride and recycling.

Example 3.-A vigorous stream of ammonia is passed at the rate of 272 liters per hour through a tube containing 500 cc. of zirconium oxide-oncarbon catalyst, which is in the form of small porous lumps. perature of 400 C. Ten hundred forty-two gm. of phthalic anhydride, is vaporized and introduced into the ammonia stream at the uniform rate of 93 gm. perv hour during a period of 11.2 The vapor stream issuing from the tube is passed into a cooled receiver where the product separates as a finely. divided powder. Water vapor is vented to aseparate trap. This powder is stirred with approximately five times its weight of warm benzene until no more of the solid dissolves. Filtration removes 152 gm. of phthalimide corresponding to 14.7% of the phthalic and thereafter extracting with cold 5% caustic soda solution to dissolve phthalimide and other alkali-soluble by-products. The mixture is filtered and the filter cake washed thoroughly with cold water and dried. If so desired, this product is further refined by distillation or sublimation.

Example 4.A vapor mixture of phthalic anhydride andammonia containing 17.7 moles of ammonia per mole of phthalic anhydride is passed over 500 cc. of a dehydrating catalyst comprising oxide-on-carbon. 1 The catalyst is maintained at a temperature of 400 C., and during a period of 12 hours a total 1217 gm. of phthalic anhydride is processed. These conditions correspond to a space velocity of 575 volumes of gas per unit volume of catalyst per hour and a contact time of 2.5 seconds. The products obtained from this reaction are worked up according to the procedure described in Example 1. There is obtained392 gm. of phthalimide. 672 gm. of orthophthalonitrile, and 9.3 gm. of benzonitrile. The molecular conversions to these products were respectively 32.5%, 63.2%,. and 1.1% of theory.

In the foregoing examples we have recited certain preferred conditions of operation. However, we wish to make it clear that our invention is capable of wide variation and modification without departing from the spirit thereof. For example, the process of this invention may be carried out at elevated catalyst temperatures in the range from about 300 to about 550 C. Sim ilarly, the molecular ratio of ammonia to phthalic anhydride may be varied considerably within practicable limits, although it is preferable to The catalyst is maintained at a tememploy ammonia ratios in the neighborhood of 15 to 20.

In the examples we have also mentioned two other important variables: space velocity and contact time. These variables, which are very closely related, serve as a measure of-the rate at which the gaseous reactants pass through the catalyst bed. Space velocity is defined as the number of volumes of gas calculated as at standard conditions that pass through a unit volume of catalyst in one hour. Time of contact is defined as the time in seconds that is required by the gaseous reactants to traverse the entire space occupied by the catalyst at the temperature and pressure of the reaction, assuming no change in volume. The time of contact and space velocity may be calculated from each other by the 7 following expression:

273 60X 60 (273+ temp. C.) X space velocity In the practice of this inventiomitis most advantageous to operate with contacttimes' rang ing from about two seconds "to about twelve seconds. 1 M I The catalysts of this invention are conveniently employed either in the form of hard, porous gels or else deposited on some suitable porous Time of contact support such as charcoal, alundum, pumice, in-

product of the reaction.

Having given a complete description of-our invention, it is to be understood that we do not limit ourselves to the specific embodiments thereof except as defined in the following claims.

We claim: 7

I 1. In the process of producing aromatic nitriles by reacting, in the gaseous phase and in'the presence of a catalyst, ammonia and a compound selected from the group consisting of aromatic carboxylic acids, their anhydrides, amides and imides, the improvement which consists of employing as catalyst a dehydrating agent selected from the group consisting of the oxides of beryllium, vanadium, zirconium and tungsten.

2. A process for the manufacture of an aryldinitrile having the two nitrile groups in adjacent positions, which comprises submitting a gaseous mixture, comprising ammonia and an aryl-dicarboxylic acid derivative 'of the general formula V Aryl \X wherein X stands for O or NH, and wherein the CO groups occupy adjacent positions, to a temperature between 300 and 550 C. in the presence of a dehydrating catalyst selected from the group consisting of the oxides of beryllium. vanadium, zirconium and tungsten.-

3. A process for the manufacture of aryl dinitriles which comprises heating a gaseous mixture comprising a molecular excess of ammonia and a member of the group consisting of orthophthalic acid, ortho-phthalic anhydride, phthal- In addition to phthalic acid 2,203,861 amic acid, phthalimide, and phthalamide at a temperature between 300 and 550 C. for a period of time between about 2 seconds and about 12 seconds in the presence of a catalyst selected from the group consisting of the oxides of beryllium, vanadium, zirconium and tungsten.

4. A process as in claim 3, in which the quantity of ammonia is at least 15 times the amount theoretically required to react with the organic compound undergoing conversion to phthalonitrile.

5. The process of producing an aromatic dinitrile, which comprises passing a gaseous mixture of ammonia and the anhydride of an aromatic dicarboxylic acid, over a catalyst maintained at a temperature between about 400 and 500 C. and being an oxide of the group of beryllium oxide, vanadium oxide, zirconium oxide and 500 C. over a catalyst selected from the 1 group consisting of the oxides of beryllium, vanadium, zirconium and tungsten, the rate of flow of gases being controlled so that the resulting contact time is between 2 and 12 seconds.

ARDEN GARREIL DEEM. WILBUR ARTHUR LAZIER. 

